Oil & Gas Pipelines
In the oil and gas sector vanadium gives steels the required strength and low temperature toughness for challenging applications, such as pipelines laid in arctic regions or those carrying sour gas.
The greatest developments have taken place in pipeline steels for gas transmission because an increase in strength can enable higher pressures to be used which dramatically reduces the cost of transporting gas. Higher strengths are also important for oil lines to reduce the wall thickness of the pipes and thus to reduce the weight of pipes and the cost of transporting the pipes to site. Where the pipelines operate at low ambient temperatures the steels must be resistant to low temperature brittleness. All steels must be weldable at the highest possible speeds without susceptibility to hydrogen cracking even when welded in regions of high humidity. For pipelines carrying sour gas the steels must be resistant to corrosion by hydrogen sulphide.
Vanadium is used in steels made to specifications involving various combinations of these properties for operation in many types of environment.
In pipelines, alongside the increasing demand of oil and gas companies for steels having higher strengths, increased low temperature toughness and a capability to be welded at higher speeds, developments have also taken place in steelmaking and rolling which have enabled higher strengths to be attained at lower carbon contents without heat treatment. The first high strength steels were supplied in the normalised condition and vanadium was added with nitrogen to give a fine grain size and precipitation strengthening. Special rolling processes which replaced the normalising enabled low carbon steels with increased weldability to be used for pipelines but they required vanadium to maintain the strength of the pipe especially in pipes with thicker walls.
Vanadium steels were used in most of the major pipelines built in the second half of the 20th century including the Alaskan oil pipeline, the trans-European pipe bringing natural gas from the Russian Arctic to western Europe and the Northern Borders pipeline carrying natural gas from Alberta, Canada to the eastern USA.
Sour gas (containing hydrogen sulphide) presents a particular corrosion problem and vanadium is used to compensate for the strength lost by using lower carbon and manganese contents in these steels.
Other relevant applications include valves and bends in pipelines which are forged and welded from plates of normalised high strength steels containing vanadium, and oil storage tanks which made by welding normalised or quenched and tempered steels which depend for their strength on vanadium carbide precipitation.